I think there have been reports here of problems both with using
rdiff-backup via samba (smb) and, independently, to a Windows
destination. By contrast, backup from Windows to Linux via ssh is well
tested and reliable - except perhaps (others may know better) when
restoring Windows ACLs.

You might like to look at my TimeDicer project
http://www.timedicer.co.uk, this uses rdiff-backup and is designed for
local network data backup from Windows with an option for secondary
offsite backup. It uses a special-purpose server based on Ubuntu and
communication is by ssh. (For offsite backup of the server it uses rsync
with ssh and --link-dest.) For file recovery it includes rdiffWeb.